(1) Field of the Invention
The present invention relates to a structure of an impact absorbing steering apparatus for an automotive vehicle.
(2) Background of the Art
A steering apparatus generally includes a steering column having a steering bracket removably supporting a column jacket from a vehicle body, the column jacket being extendable and contractable in its axial direction so that a vehicle occupant can be protected from a secondary collision against the steering apparatus after collision with a moving or stationary obstacle.
In this case, the bracket has a U-shaped groove opened toward an upper end portion thereof and is fixed to the vehicle body by means of a bolt fitted into the groove. Therefore, if impact is received by the column jacket from the occupant, the bracket slides downward leaving the bolt. However, it is difficult for the column jacket to smoothly detach from the vehicle body in a case where shock from a direction other than the axial direction of the column is applied to the column jacket.
A Japanese Utility Model Registration First Publication No. Showa 52-55535 published on Apr. 20, 1977 (filed on Dec. 20, 1975) exemplifies a previously proposed structure of an impact absorbing steering apparatus in which a cut out portion in a substantially horizontal direction intersecting with the column jacket is previously formed on the bracket so that shock energy may be absorbed by tearing off the cut out portion when an excessive force is applied to the column jacket. Since secondary collision generates a force which pushes from the upper end portion of the column jacket toward the front of the vehicle body, the bracket linking the column jacket is supported on a clamp fixed to the vehicle body with merely a plurality of spot welded portions.
However, in the previously proposed structure of the steering apparatus disclosed in the above-identified Japanese Utility Model Registration First publication, the bracket may be detached from the clamp if the spot welded portions are snapped due to shock upon vehicle collision. At this time, the shock absorbing effect induced by the tearing off of the cut out portion is pre-empted and therefore of no benefit to the vehicle driver.
On the other hand, in another previously proposed steering apparatus, another steering column having the bracket, the bracket including a front wall to which the column jacket is perpendicularly fixed, a curl portion formed on both side ends of the front wall by bending thereof at a predetermined curvature, a roller inserted into the curl portion, both side portions extended in parallel to the column jacket from the curl portion, and cut out portions formed respectively on the both side portions. The bracket is fixed on a clamp fixed to the vehicle body. In a case where impact is received by the column jacket in the axial direction, the bracket generates curling and ripping so as to absorb the shock energy.
However, since in the above previously proposed steering apparatus a steering shaft and its universal joints are arranged within the jacket enclosing the clamp and bracket, the rotation of the steering shaft could be blocked or canceled by foreign matter (e.g., a bolt or coin placed on an instrument panel) slipping into the inside of the bracket or dropped thereinto.
Also, in the steering column in which curling and ripping are generated, foreign matter dropped into the bracket as described above could inhibit the curling and ripping action so that the shock energy cannot be absorbed.